Loading .357 brass to .38spl pressures?


March 8, 2009, 07:37 AM
I have been loading .38 rounds for a few weeks (my first reloading attempt) with good results. I am now interested in loading .357 brass to light .38 balistics to get rid of leading in my cylinders. Can I use the same load (5.7gr 231 with a 25gr bullet) in the .357 brass, or with the longer lenghth of the .357 cause problems with a light load such as this?

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March 8, 2009, 08:50 AM
I'm going to assume you meant 125g bullet and not 25g bullet (What the heck would that look like? A button?) I'm also going to assume that you found that data published somewhere, because it's .2g higher than Hodgdon's published 357mag loads for a 125g bullet. The above given, yes, you're fine. You might lose just the tiniest smidge of velocity due to a larger case capacity, but you won't notice the effect at target distances.

The rule of thumb I was taught, when jumping to longer brass with the same load, add 10% powder to make up for added capacity and volume, need not apply here as that's not a slouch 38 load.

March 8, 2009, 09:08 AM
I'm going to assume that you meant 125 gr bullets also, and if this is correct your charge of 231 is way below the starting charge for a 357. The current Speer Manual #14 shows a starting load of 7.6 gr of 231 for a 125 gr bullet. It can be dangerous to load ammo below recommended starting weights of fast powder. Please obtain one, or even better, several loading manuals and follow their advice. If you want to shoot lighter loads, stick with the 38's. We want to keep you safe! :uhoh:

The Bushmaster
March 8, 2009, 10:15 AM
If it is a .357 magnum case...Load it as a .357 magnum. If it is a .38 Special case...Load it as a .38 Special. Do not interchange cases and load data.

If you don't want leading at the cylinder mouth change to plated or jacketed bullets. You will still have carbon forming at the cylinder mouth and will still have to clean it out, but that's part of the game...

March 8, 2009, 11:42 AM
Not trying to hijack the thread, but I have a question that is (kind of) relavent, as I've been considering the same. I'm just waiting on finding primers before getting started.

I understand the whole capacity, powder charge, pressure situation. I.E. too much unused space (reduced loads with fast powder) can produce an increased "spike" in pressure.

The question is this...Can you do, as the OP asked, and load a .357 with a .38 charge, but instead of loading to an OAL of the .357, seat the bullet that little bit deeper and have an OAL equal to a .38 Spec? Will this make pressures unsafe? I really don't see why, but I'm just learning here also, and wanted to ask the experts.

I've been considering doing this for practice loads only, but carrying full mag loads. I just want to maximize my trigger time with my new carry revo.

Sorry again if this is considered hijacking, but again, I see it as a relevant question to add to the OP's question.


March 8, 2009, 12:34 PM
I have tried deep seating bullets in .357 mag cases when loading to .38 Spl levels, and found it a waste of time. (IMHO of course)

I shoot 125, 148, & 158 Gr bullets in .357 cases loaded to .38 Spl levels. (140's soon) I have found that when using fast powders (Clays, Red Dot, etc) that at most the .357 case needs .1 grs more powder than the proven load in .38 Spl brass.

I would assume that as the burn rate gets slower that would increase to .2 or maybe even .3 grs for some powders.

Since that is such a light load, I would start with 5.8 Grs of W-231 to start, and go from there.

If you were getting leading you may be too light for the hardness of the bullet you are using. Switching to .357 brass won't stop that. If you are talking about carbon buildup from using .38 brass in a .357, that is just life in the fast lane. That is the main reason I use .357 brass for .38 Spl loads in .357's though.

March 8, 2009, 12:55 PM
What I have been doing is loading 38's in 357 brass loaded to 357 length. I use Bullseye for powder and just add 1-1.5 grain to my 38 load in 357 brass. I believe I heard somewhere that it was safe to do this-load 38 in 357 brass or 44spl in 44mag brass just by adding 5-10% to the lesser round in the longer case. The only real advantages are being easier to clean and less recoil.

Standard advice is to reference at least 3 manuals then do whatever Walkalong or RC advises. :neener:

March 8, 2009, 03:19 PM
Not exactly what was asked because the question is supposedly about 125 grain bullets and W231, but you might want to buy a pound of Unique. 8 grains of Unique behind a 125 grain bullet in a .357 Mag case is a relatively light load and it doesn't seem to be too dirty. Though I use H110/W296 for full power loads, I prefer the lighter Unique loads for practice.

March 8, 2009, 03:44 PM
With 44mag what I do is take a 44spl load using Unique, add 1-2gr of powder and put it in a 44mag shell.
I get hot 44spl / light 44mag rounds that burn real clean.
Unique burns very clean as long as you dont light load it.

Steve C
March 8, 2009, 04:09 PM
There's no downside to downloading the magnum cartridge to the non magnum level as lower pressure in any magnum pistol is certainly safe. The reverse, uploading a non magnum to magnum level is unwise as one of these high pressure cartridges may find its way into a non magnum pistol.

A load of 5.7gr with a 125gr jacketed bullet in the .38 spl is over max +P in most data I've checked. If using a 125gr cast its over the top end of Cowboy loads in the .357 mag (Hodgdon data). In the .357 mag it would be fine with hard cast or jacketed bullets.

There's not enough significant differences between the capacity of the .357 magnum case vrs the .38 spl case to prevent using .38 spl data in the magnum. The reason the start loading in the magnum is well above 5.7grs (for jacketed bullets) in the magnum is because its a start load to produce magnum velocity and pressure and not a minimum based on any safety requiremnt.

March 8, 2009, 04:11 PM
There's plenty of .357 load data for light loads. I use 7.6gr of Unique under a 125gr jhp and standard primers. This load is what is 99% of my shooting in that gun.

March 8, 2009, 06:14 PM
go to the hodgdon site plenty of low pressure loads or look on any data site under cowboy loads.


March 8, 2009, 09:04 PM
I shoot mid range .38 loads in .357 cases all the time with no problems. The only problem I've had was trying light loads of Unique that caused several squibs.

March 9, 2009, 03:36 AM
Thanks for the advise. The bullet is 125 gr, not 25 gr... Given the various view points here, I think I will ere on the side of safety and wait till I can find some published load info for very light .357 rounds...

I REALLY want to find some unique powder, but reloading supplies have been imposible to find around here since PBO got elected.

March 9, 2009, 04:14 AM
I REALLY want to find some unique powder, but reloading supplies have been impossible to find around here since PBO got elected.
If you're looking for a cleaner over all load Unique isn't the powder you're looking for, especially in a load that's on the light side. IMO you should use W231/HP-38 or Clays to keep things nice and clean.

About the powder charges, using a 125gr LRN bullet the Min/Max charge numbers for the .38 Special using W231 are 3.8gr and 4.8gr. The charges for the same bullet and powder in a .357 Magnum case are 4.6gr and 5.5gr. You can load the .357 Magnum to the Min charge and be below the Max charge of a .38 Special.

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